Feed microscopy -: its special relevance for veterinary nutrition

Feed microscopy includes different techniques which give information on the quality of ingredients, premixes and concentrates (complete diets) by visual inspection. For this purpose binocular magnifiers (magnification: 15-60) and microscopes (100-300 magn) are in use. The aims of feed microscopy are: identification of ingredients using morphological and histological signs of cells and tissues and their surface; incrustations; estimation of the proportion of ingredients in the mixture; the detection of contaminants such as toxic seeds, moulds, insects and mites. For this purpose special preparations (for example coloured cuts) of the feed samples are frequently needed (for example for histological inspection). As a first step, visual inspection of feeds using a binocular magnifier can give rough information on the presence of mites, moulds, undeclared ingredients, contaminants like ergot and excess of minerals or trace elements. If there are suspicious findings, microscopic examination by experts is recommended. Several cases are presented, in which the probable cause of feed-related problems was found ty iced microscopy. In samples of cereals and concentrates send to the authors' institutes a massive contamination by mires and insects was frequently observed (10 % of samples during summer). The refusal of a new lot of concentrate was often caused by unusually high proportions of rape seed, legumes, blood meal and other ingredients. The use of faba beans resulted temporarily diarrhoea in pigs. Toxic seeds like Bassia or Sinapis spp resulted in diarrhoea in co ws. In 44 of 269 (approximately 16.4 %) samples of concentrates for cows and 80 of 969 (8.3 %) samples of concentrates Far pigs the type and/or proportions of ingredients in the concentrate were not in accordance with the declared values. Based on the experience gained over the last 10 years it is concluded that feed microscopy is a key part of feed quality control and has a special relevance to veterinary nutrition.